The present invention relates to the construction of nozzles for combining two gases and, more particulary, the invention relates to the construction of nozzles by means of which different gases are injected and charged into the optical cavity of a chemical laser.
A chemical laser is, for example, constructed to have two major sections. In one section, a preparatory reaction takes place, including, for example an in situ thermal dissociation of molecules in order to obtain a certain quantity of atoms, e.g., of a halogen such as fluorine. The gaseous substance as prepared in this chamber is commonly referred to as the oxidizer or primary fluid. The nature of the preparation of the oxidizer involves raising its temperature and pressure, and the preparation process is in some cases a combustion, so that the chamber, in which this process takes place, is called a combustion chamber. The other section includes the optical cavity as well as optical outputcoupling devices, etc., for the laser. The optical cavity of the chemical laser receives the oxidizer as well as fuel. The reaction in the optical cavity between the fuel and the oxidizer produces a laser-active medium.
The two sections are, so to speak, interconnected by means of a nozzle structure, causing the oxidizer, as developed in the reaction chamber of the first section, to be mixed with fuel gas and, possibly, others to obtain the requisite temperature and population inversion in the optical cavity by means of a chemical reaction or reactions as between oxidizer and fuel. A common chemical laser involves fluorine, and the combustion causes dissociation of a substantial amount of fluorine molecules into fluorine atoms, serving as the oxidizer proper. A mixture of atomic and molecular fluorine together with residue of the combustion process as well as e.g. helium or nitrogen as a diluent is charged into the optical cavity by means of a primary nozzle or nozzles; commonly, hydrogen or deuterium is used as fuel and is charged through secondary nozzles into the optical cavity, to mix and react with the oxidizer.
Two major events occur and are established by such a dualcharge process of the optical cavity: (a) the primary nozzle establishes supersonic flow of the oxidizer into the cavity under conditions of flow expansion in order to obtain the requisite thermodynamic conditions for the subsequent chemical laser action; and (b) the oxidizer and fuel gases, being separately discharged by the primary and secondary nozzle structure into the laser cavity, must mix intimately. These two requirements must not only be compatible, but (i) the several gases, as they are mixed, must have the requisite stoichiometric proportion in the instant the thermodynamic conditions are "right" for the chemical reaction and for the lasting action; and (ii) these composite conditions must concur over a fairly large zone in the laser cavity, simply to obtain a high optical power yield.
It is believed that the known nozzles and nozzle structure are deficient in performance, ultimately, as far as the condition and requirement (ii) is concerned. The expanding flow of the oxidizer, as it meets the fuel, will, of course, establish the correct combination of parameters for laser action at some point in the optical cavity, even if the operating conditions vary over a wide range. However, that alone is clearly insufficient. One needs a large zone (volume) filled with a laser-active substance in order to obtain an optical power yield commensurate with the effort expanded for establishing the various conditions, including a large rate of dissociation for obtaining a large quantity of oxidizers, which, of course, should be used and used up to the fullest extent possible.
Another drawback of the prior art nozzles for charging the optical cavity is the need for adding extensive quantities of dilutents (e.g., helium) to the oxidizer in order to match the thermodynamic conditions of the combustion products with the thermodynamic requirements in the laser cavity. The prior art nozzles through which the oxidizer is discharged from the combustion chamber are further disadvantages by their structure. These nozzles project into the combustion chamber to a considerable extent, thus offering a relatively large surface for the influx of heat which has to be removed. Extensive internal cooling of the nozzles, however, extracts heat from the combustion chamber which is thus removed therefrom and "wasted."